Neoplastic transformation produces many changes in cell physiology. We have utilized morphologic techniques to study these changes and to understand certain basic cellular mechanisms of motility, organelle movement, and compartmentalization of intracellular materials. We have employed ultrastructural immunocytochemistry, single cell microinjection, and image intensification techniques to follow the movement of substances through various endocytic and exocytic compartments within the cell, as well as the cytoplasmic structures mediating movements of the entire cell and its subcellular organelles. These include localization of the endocytosis of external macromolecules and the receptors which bind them, particularly those for epidermal growth factor, transferrin, lysosomal enzymes and alpha2-macroglobulin. We have also followed the exocytosis exocytosis of Vesicular Stomatitis Virus G protein, as well as the transit of epidermal growth factor through the Golgi system. These results have demonstrated that the clathrin-coated pits of the Golgi system are involved in transfer of materials into lysosomes, but are not involved in exocytosis. Preliminary studies have been conducted on the movement of organelles in living cells using microinjection of antibodies with image intensification and electron microscopy.